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    <title>Document</title>
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    <script>
        var foo = function(){};
        var a = 3;
        let b = 2;
        console.log(this)
        function person(){
            console.log(this)
            console.log(this instanceof foo)    //false， 通过new关键字绑定的this和foo不在一个原型上
        };

        new person();

    </script>
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